1. Field of the Invention
Implementations of various technologies described herein generally relate to seismic data acquisition.
2. Description of the Related Art
The following descriptions and examples are not admitted to be prior art by virtue of their inclusion within this section.
In a typical seismic survey, a plurality of seismic sources may be activated to generate energy which may be reflected back by the earth's sub-surface layers. The resultant seismic wavefield may be sampled by an array of seismic sensors deployed at a distance from the seismic source. Each sensor may be configured to acquire seismic data, normally in the form of a record or trace representing the value of some characteristic of the seismic wavefield against time. Typically, a plurality of sensors is arranged in a grid, such that the recorded data from the wavefields may substantially cover the entire area of exploration with sufficient resolution to detect the variation of the sub-surface structure over small spatial distances. The acquired seismic data may be transmitted over electrical or optical cables to a recorder system. The recorder system may then store, analyze, and/or transmit the data.
Large seismic sensor arrays are becoming typical. The larger the array, the greater the deployment time and cost of equipment may be for the survey. Wireless seismic sensor arrays have been attempted to help minimize deployment time and cost of equipment.
Typical wireless approaches use a variety of communication protocols, such as:                GSM-DCS, or Global System for Mobile Communications-Digital Cellular System, which employs a form of time-division multiplexing called Time Division Multiple Access (TDMA);        UMTS, or Universal Mobile Telecommunications System, which may be used to deliver broadband information at speeds up to 2 Mbps to wireless devices anywhere in the world through fixed, wireless and satellite systems;        DECT, or Digitally Encoded Cordless Telecommunications, which is a common standard for cordless personal telephones;        CDMA, or Code-Division Multiple Access, which is a digital cellular technology that uses spread-spectrum techniques; and        GPRS, or General Packet Radio Service, which is a standard for wireless communications and runs at speeds up to 115 Kbps and supports a wide range of bandwidths.        
However, the application of each of these protocols brings its own problems. For example, UMTS, DECT and CDMA are telephone oriented, rather than network oriented, which imposes undesirable restrictions on communication of seismic data. UMTS and GSM have the same upstream and downstream bandwidth, but in seismic acquisition a much higher upstream bandwidth is needed than downstream bandwidth. GPRS allocates more than one channel downstream and sometimes none upstream, which is counter to the needs in a seismic acquisition system. GSM-DCS typically makes poor use of the number of channels in a cell versus the possible range of the cell because of a disparity between the density of the sensors in the cell and the surface area of the cell. Additionally, GSM-DSC employs a wire between its base transceiver unit and the Basic Station Controller as well as between the Basic Station Controller and the central recording and processing system. As such, although costs savings can be realized with wireless systems, typical wireless techniques applied in seismic acquisition need improvement.